1. Field of the Invention
The present invention relates to a switch device, and more particularly to a structure of a rotary switch device having a click mechanism which is used in various electronic equipment for household or vehicle mounting.
2. Description of the Prior Art
A structure of a conventional rotary switch device having a click mechanism is shown in FIG. 5. FIG. 5 is an exploded perspective view of the rotary switch device.
This conventional rotary switch device includes a resin-made housing 11 which has a support shaft 11a at the center of an accommodating portion 11b, a fixed terminal portion 12 which is arranged in the accommodating portion 11b of the housing 11, a circuit board 13 which has a contact portion which is brought into slide contact with a slider 12a of the fixed terminal portion 12, a rotary manipulating portion 14 which has the circuit board 13 fixedly secured to a lower surface side thereof, is rotatably supported on the support shaft 11a of the housing 11 and has a cam surface 14a which alternately forms plateaus and valleys on an upper surface thereof, a spring member 15 which is disposed such that the spring member 15 faces the cam surface 14a in an opposed manner and has a projection 15a which is brought into slide contact with the cam surface 14a, and a frame 16 which has a lower surface side thereof to which the spring member 15 is fixedly secured and is fitted on an upper surface side of the housing 11.
A click mechanism of this rotary switch device is comprised of the cam surface 14a which is formed on the upper surface side of the rotary manipulation portion 14 and is constituted of the plateaus and the valleys, and the spring member 15 which has the projection 15a which is brought into slide contact with the cam surface 14a. To manipulate the rotary switch device, a rotary manipulation tab not shown in the drawing which is protruded from the frame 16, is mounted on the upper surface side of the rotary manipulating portion 14 and is rotatably manipulated with a hand or the like. Along with the rotation of the rotary manipulating portion 14, the projection 15a is moved between the plateau and the valley and when the projection 15a gets over the plateau and falls in the valley, the spring member 15 is deflected so that a click feeling is generated.
Then, along with the rotation of the rotary manipulating portion 14, the contact portion which is disposed at the circuit board 13 is brought into slide contact with the slider 12a of the fixed terminal portion 12 which is disposed such that the slider 12a faces the contact portion in an opposed manner so as to perform the switching of a circuit.
However, in the abovementioned constitution of the conventional rotary switch device, when the rotary manipulating portion 14 is manipulated, at a point of time that the projection 15a of the spring member 15 is slidably moved on the plateaus and the valleys of the cam surface 14a and falls in the valley after getting over the plateau, the projection 15a suddenly impinges on the cam surface or generates vibration due to the resiliency of the spring member 15 so that there has been a drawback that the a switching sound (an impinging sound) at the time of manipulation is large.
Accordingly, the present invention has been made to solve the abovementioned drawback and it is an object of the present invention to provide a switch device which can reduce or attenuate a switching sound (an impinging sound) at the time of manipulation with a constitution of a click mechanism which uses a spring member having a projection which is brought into slide contact with a cam surface formed of plateaus and valleys.
To solve the abovementioned drawbacks, according to a first aspect of the present invention, there is provided a switch device which includes a housing having an accommodating portion, a manipulating member having a cam surface which is formed of plateaus and valleys arranged contiguously and alternately, the manipulating member movably disposed in the accommodating portion, and a spring member having a projection and generating a click feeling when the projection is brought into slide contact with the plateaus and the valleys of the cam surface, wherein an auxiliary spring which is brought into slide contact with the manipulating member corresponding to the slide contact of the projection with the plateaus and the valleys of the cam surface is formed on the spring member, wherein and an auxiliary spring receiving portion with which the auxiliary spring is brought into slide contact is formed in the vicinity of the cam surface.
According to a second aspect of the present invention, the auxiliary spring is integrally formed with one end of the spring member by forming a portion of the spring member.
According to a third aspect of the present invention, the auxiliary spring is formed such that a pressing force applied to the auxiliary spring receiving portion becomes maximum when the projection is engaged with the valley of the cam surface.
According to a fourth aspect of the present invention, the auxiliary spring receiving portion is formed on the manipulating member such that the auxiliary spring receiving portion forms an integral coplanar surface with the cam surface.
According to a fifth aspect of the present invention, the auxiliary spring is formed such that the auxiliary spring is in a slidable contact in the state that the auxiliary spring always stays in contact with the planar auxiliary spring receiving portion when the manipulating member is moved.
According to a sixth aspect of the present invention, a support shaft formed in a cylindrical shape is mounted on the center of the accommodating portion of the housing, the manipulating member allows insertion of the support shaft thereinto and is rotatably supported by the support shaft, the cam surface and the spring member having the projection which faces the cam surface in an opposed manner are disposed in a vertical direction relative to the support shaft, and a portion of the spring member is extended along a circumferential direction of rotation of the manipulating member from a position in the vicinity of the projection so as to form the auxiliary spring, and a free end of the auxiliary spring is brought into contact with the auxiliary spring receiving portion.
According to a seventh aspect of the present invention, the auxiliary spring is symmetrically extended toward both sides of the circumferential direction of the rotation of the manipulating member with respect to the projection.